FIGS. 10 and 11 show a fuel processor of Patent Literature 1. An arrow F indicates a direction of a gas flow.
A fuel processor 1 is entirely cylindrical and includes a heat insulator 1a that covers the outer surface of the fuel processor 1 to provide heat insulation. A heater 5 is provided at the center of the fuel processor 1 and includes a heat chamber 3 that contains a burner 2 and an exhaust gas passage 4 that surrounds the heat chamber 3. The exhaust gas passage 4 includes an outlet port 4a opened to the outside to discharge exhaust gas 74. Furthermore, a first gas passage 6 acting as an evaporator is disposed around the outlet side of the exhaust gas passage 4 of the heater 5. A reformer 8 filled with a reforming catalyst 7 is disposed around a part where hot exhaust gas flows from the heat chamber 3 to the exhaust gas passage 4. The reforming catalyst 7 is fed between an internal cylinder 18 and an external cylinder 19. The reformer 8 is surrounded by a second gas passage 9 that passes hydrogen containing gas from the reformer 8 to the outer surface of the first gas passage 6. Moreover, a converter 11 filled with a CO converter catalyst 10 is disposed near the reformer 8 on the outer surface of the first gas passage 6 while a CO remover 14 filled with a CO removal catalyst 13 is disposed far from the reformer 8 on the outer surface of the first gas passage 6 so as to be located outside a third gas passage 12 in a radial direction, the third gas passage 12 being disposed inside the CO remover 14 in the radial direction.
Fuel gas 70 is supplied into an inlet port 6a of the first gas passage 6. The supplied fuel gas 70 is mixed at the inlet port 6a with reformed water 72 supplied through a heating coil 15 wound around the converter 11 and the CO remover 14. The fuel gas 70 and the reformed water 72 are heated through the first gas passage 6 acting as an evaporator. The high-temperature fuel gas and steam are supplied to the reformer 8, and then the fuel gas is steam reformed by the action of the reforming catalyst 7 into hydrogen-rich gas.
The hydrogen containing gas fed from the reformer 8 is supplied to the converter 11 through the second gas passage 9, and then carbon monoxide (CO) in the hydrogen containing gas is reduced by the action of the CO converter catalyst 10. The hydrogen containing gas fed from the converter 11 is mixed with air 71, which is introduced from an air inlet port 16a, in an air mixing space 16 provided between the converter 11 and the third gas passage 12. The hydrogen containing gas mixed with the air 71 is supplied to the CO remover 14 through the third gas passage 12, CO is removed from the gas by the action of the CO removal catalyst 13, and then hydrogen containing gas 73 is fed from a hydrogen-containing-gas outlet port 17.
The third gas passage 12 is provided between the CO remover 14 and the first gas passage 6 at a high temperature. Thus, a temperature downstream of the converter 11 can be kept at an optimum temperature for a reaction (e.g., 200° C.); meanwhile, the inlet temperature of the CO remover 14 can be kept at a temperature (e.g., 150° C.) where an oxidation reaction is not excessively accelerated. In other words, the converter 11 and the CO remover 14 can be advantageously kept at a suitable temperature.
FIG. 11 is an enlarged view of the reformer 8 described in Patent Literature 1.
The reformer 8 contains the reforming catalyst 7 shaped like spherical or cylindrical particles that are fed by vibrations or the like with maximum density into a catalyst layer 21 surrounded by the internal cylinder 18, the external cylinder 19, and partition plates 20. The reformer 8 needs to have at least a certain length in the axial direction with respect to the width of the reformer 8 in the radial direction because a proper passage distance is necessary for completing a reforming reaction. Thus, the reformer 8 is relatively extended in the axial direction. A load caused by the weight of the reforming catalyst 7 increases toward the bottom of the reformer 8. Moreover, the thermal expansion of the external wall of the heater 5 in contact with the reforming catalyst 7 may cause deterioration, e.g., a crush of the reforming catalyst 7 under a pressure or powdering on the surface of the reforming catalyst 7. Thus, the partition plates 20 are provided at regular intervals in the axial direction to disperse the load of the weight of the reforming catalyst 7, preventing deterioration such as a crush. This configuration is described also in Patent Literature 2 and Patent Literature 4.
FIG. 12 illustrates the structure of the reformer 8 of the fuel processor 1 in consideration of actual production.
When fuel gas is reformed into hydrogen-rich gas by steam reforming, the reformed gas can be efficiently refined by heating the reforming catalyst 7 to a desired temperature (e.g., 450° C. to 700° C.). Thus, the catalyst layer 21 is located near the bottom (high-temperature part) of the internal cylinder 18 so as to be easily heated by the heater 5. The partition plates 20 are attached by welding to the outer surface of the internal cylinder 18 other than a partition plate 20a at the bottom such that a welding torch can be set in the absence of the external cylinder 19 and heat is further transmitted from the heater 5 to the reforming catalyst 7. However, the temperature of a high-temperature part 18a of the internal cylinder 18 is increased to the maximum temperature (e.g., 750° C.) of the overall reformer 8. Thus, a fuel cell is repeatedly started and stopped so as to repeat thermal expansion and thermal shrinkage in a cycle of great temperature variations, resulting in a severe environment that is likely to cause a fatigue fracture on a welded part. The partition plate 20a attached at the bottom to the high-temperature part 18a of the internal cylinder 18 by welding may be dropped by a fatigue fracture in repeated operations. For example, in Patent Literature 3, the attachment of a reinforcing member to the partition plate is proposed to prevent a catalyst from dropping because the partition plate may drop the catalyst when being pressed down by the resistance of the catalyst during thermal shrinkage.
Hence, in the structure of FIG. 12, the end of the external cylinder 19 is located around the catalyst layer, and the partition plate 20a at the bottom is attached to the inner surface of the external cylinder 19 by welding. This allows the attachment of the welding torch enabling welding. Since the external cylinder 19 is set at a lower temperature than the internal cylinder 18, the partition plates 20 are less likely to drop.